In general, an OCR (optical character recognition) process is executed on a character image acquired by reading a character written on paper by a scanner. In recent years, with an increase in resolution of cameras, an application is available which corrects a character image photographed by a camera, and executes an OCR process on the corrected character image.
Identification determination of an object in a plurality of images photographed at different positions is executed by a trigonometrical survey, if photography positions and photography directions of plural cameras are already known. On the other hand, when photographing an object while moving one camera at an unfixed speed, the photography position and photography direction of the camera are variable. Thus, even if a calculation by a trigonometrical survey is tried, an error becomes larger and it is highly possible that a correct result is not obtained. This being the case, as methods of determining an identical object, there are methods such as a determination method by characteristic point matching, or a determination method based on a unique ID (identification) (e.g. a character string, a bar code, or a numeral string) described on the object.
However, in the method by characteristic point matching, if an object is not characteristic, compared to the surrounding condition, the characteristic point itself cannot be obtained. Furthermore, an attempt to acquire many characteristic points in order to acquire characteristic points of the object leads to erroneous determination or a decrease in processing speed.
On the other hand, in the determination method based on the ID described on the object, the ID has to be photographed with a high resolution. However, if the object is photographed by an ordinary camera from a distant point, the camera cannot photograph the ID with a high resolution. In order to photograph the ID with a high resolution, it is necessary to increase the resolution of the camera or to narrow the view angle. Consequently, the cost will increase and the operability will deteriorate.
Besides, in the OCR process for a character image acquired by a camera, the recognition ratio of characters for a low-resolution character image extremely decreases. Moreover, as regards a low-resolution character image, the recognition ratio of characters tends to vary depending on the quality of images. The quality of images greatly varies due to a slight difference in photography conditions, such as a photography timing of a character image, a photography position, and a photography environment (illumination).